Power focus device for a camera

ABSTRACT

A power focus device for a camera provides a user-friendly lever interface allowing efficient camera operation. A lever, located outside a camera cover, is movable in two opposing directions but is biased to remain at a neutral position between two extremes of movement. Moving the lever from the neutral position initiates driving the camera lens to focus in either a first or a second direction according to a direction of a displacement of the lever from the neutral position. A speed of focusing is proportional to an amount of displacement of the lever from the neutral position, thus permitting variable high and low speed focusing in both directions for rapid and accurate close-up and infinity focussing. Incorporating a seal into the device permits use in underwater camera applications.

This application is a continuation of application Ser. No. 08/384,952,filed Feb. 7, 1995, which is a continuation of application Ser. No.08/002,475 filed on Jan. 8, 1993, now U.S. Pat. No. 5,412,445.

BACKGROUND OF THE INVENTION

The present invention relates to a power focus device for a camera, andmore particularly, to a power focus device for focusing a lens by meansof an electric motor drive responsive to a spring biased lever control.The invention is especially useful in underwater camera applications.

Power focus mechanisms having a lens focused by a motor drive mechanismhave been proposed employing a variety of control schemes.

Japanese hid-open Patent Publication No. 63-177118 discloses a powerfocus mechanism employing a rotating control dial. Rotating the controldial generates pulse signals, whose frequency and count are produced inaccordance with rotation of the dial. The pulse signals are used tocontrol an electric motor for adjustment of a lens. The direction andspeed of adjustment of the lens is controlled by the direction and thespeed of rotation of the dial. Such a mechanism necessitates placementof the dial on the outside of the camera so that it may be operatedmanually. The need to have an exposed rotatable dial makes this approachunsuitable for applications in an underwater camera because duringoperation, it is necessary to rotate the dial many times in order toachieve a proper focus. Such manual operation results in user fatigueand detracts from the utility of the control mechanism.

Japanese Laid-open Patent Publication No. 59-64816 aim discloses a powerfocus device using first and second button switches. The lens is focusedin a first direction while the first button is depressed and in a seconddirection while the second button is depressed. Such a control mechanismlends itself to sealing by pliable switch covers. However, such amechanism does not permit real-time operation of the camera lens. Themechanism has only two switches corresponding to each of the twodirections. Each switch drives the lens at a constant speed in its givendirection. This speed may be either too slow for large focus adjustmentsor too fast for fine focus adjustments. Providing dual speeds in eachdirection offers greater flexibility but complicates the operation ofsuch a control. A user operating a dual speed control must first selectone speed to effect a large change in focus and then shift to a slowerspeed to effect a fine focus adjustment.

Thus, there exists a need for a power focus mechanism that can be easilysealed for applications involving underwater cameras while allowingvariable speed operation of the lens focusing mechanism. Furthermore,such a mechanism must provide for ease of manual operation so thatfocusing may be readily accomplished without subjecting the user tofatigue.

OBJECT AND SUMMARY OF THE INVENTION

An object of the present invention is to provide a power focus devicefor a camera that overcomes the drawbacks of the prior art.

A further object of the present invention is to provide a power focusdevice for a camera that provides a user-friendly interface whichminimizes fatigue during operation.

A still further object of the present invention is to provide a powerfocus device for a camera suitable for underwater camera applications.

Briefly stated, the present invention provides a power focus device fora camera having a user-friendly lever interface for efficient cameraoperation. A lever, located outside a camera cover, is movable in twoopposing directions and is biased so as to remain at a neutral positionbetween two extremes of movement. Moving the lever from the neutralposition initiates driving the camera lens to focus in either a first ora second direction according to a direction of a displacement of thelever from the neutral position. A speed of focusing is proportional toan amount of displacement of the lever from the neutral position, thuspermitting variable high and low speed focusing in both directions forrapid and accurate close-up and infinity focussing. Incorporating a sealinto the device permits use in underwater camera applications.

According to an embodiment of the present invention there is provided apower focus device for a camera comprising: a rotatable member capableof rotation within a fixed angular range, a means for biasing therotatable member in a neutral position allowing rotation in a first anda second direction, a position of the rotatable member within the fixedangular range defining an angle relative to the neutral position, meansfor outputting an electric signal related to the angle, means fordriving the lens to a nearest and an infinite extreme when the rotatablemember moves in the first direction and the second directionrespectively, and means for varying a driving speed of the means fordriving based upon the electrical signal.

According to another embodiment of the present invention there isprovided a power focus device for focusing a lens of a cameracomprising: means for generating a signal in relation to a position of afirst member, means for bilaterally biasing the first member in aneutral position such that the first member may be moved from theneutral position in both a first and a second direction, drive means fordriving the lens in a first focusing direction and a second focusingdirection, the drive means being responsive to the signal such that thelens is inactive when the first member is in the neutral position, andthe drive means being responsive to the signal such that the lens isdriven in one of the first focusing direction and the second focusingdirection in response to a displacement of the first member from theneutral position in one of the first and second directions respectively.

The above, and other objects, features and advantages of the presentinvention will become apparent from the following description read inconjunction with the accompanying drawings, in which like referencenumerals designate the same elements.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a first part of an embodiment of a switchof the present invention.

FIG. 2 is a sectional view of a second part of the embodiment of theswitch of FIG. 1.

FIG. 3 is an exploded view showing the structure of the switch of thepresent invention illustrated in FIGS. 1 and 2.

FIG. 4 is a schematic diagram of an embodiment of the present invention.

FIG. 5 is a schematic view of a resistive divider network included in aplan view of a substrate circuit layout of an embodiment of the presentinvention.

FIG. 6 is a graph showing the relationship between a driving directionand velocity and a position of brush contacts on the resistive dividernetwork of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a switch has a first spin lever 2 rotatably mountedon shaft la which is integrally formed in a camera body 1. Restrictinglevers 3 and 4, biased by a spring 5, are situated above first spinlever 2. Spring 5 is secured in place by a collar 6. First spring lever2 has a cylinder portion 2d extending along shaft 1a. Cylinder portion2d engages a collar 9a of a brush mount board 9 such that brush mountboard 9 rotates with first spring lever 2.

Brush mount board 9 has a brush 8 mounted upon its lower surface. Brush8 has two contacts which engage printed circuit traces on substrate 7. Acap screw 10 screws into shaft 1a to retain brush mount board 9 and theremainder of the switch assembly. The switch produces an electric signalwhich is varied by the movement of brush 8 along the surface ofsubstrate 7. The electric signal effects control of an electric motordriving a lens so that lens may be focused.

Referring to FIG. 2, first spin lever 2 has a protrusion 2a engaging ayoke end 11a of a second spin lever 11. A first end of a shaft 12 isfixed in an opposing end of spin lever 11. Shaft 12 passes through anaperture in a camera cover 14. An operating lever 13 engages a secondend of shaft 12 outside camera cover 14. An O-ring 15 is compressedbetween shaft 12 and camera cover bushing 14a, sealing passage of shaft12 through camera cover 14 and preventing leakage of water into cameracover 14. In view of this specification, it would be recognized thatother embodiments of the present invention may employ alternative meansof sealing such as pliable switch covers, made of rubber or a similarsynthetic material, which permit required angular range of motion ofoperating lever 13.

Deflection of operating lever 13 outside camera cover 14 rotates spinlever 11 inside camera cover 14 which in turn rotates first spin lever 2by engagement of protrusion 2a with yoke end 11a of spin lever 11.

Referring back to FIG. 1, rotation of first spin lever 2 rotates brushmount board 9 which moves brush 8 on substrate 7. Movement of brush 8produces an electrical signal for controlling operation of the motorfocusing the lens.

Referring to FIG. 3, first spin lever 2 is biased by spring 5 andrestricting levers 3 and 4 so as to remain in a neutral position, asshown in FIG. 3. In the neutral position first spin lever 2 has a centerline parallel to line L. Force exerted upon first spin lever 2 by spinlever 11 displaces first spin lever 2 through a limited angular range ineither a clockwise or a counter-clockwise direction. Spring 5 returnsfirst spin lever 2 to its neutal position when external force isremoved.

Spring 5, with arms 5a and 5b, is situated above restricting levers 3and 4 biasing first spring lever 2 into a neutral position. Arms 5a and5b engage tabs 3b and 4b of restricting levers 3 and 4, respectively.Restricting levers 3 and 4 have hand portions 3a and 4a which rest uponstops 1c and 1b, respectively. Stops 1c and 1b are incorporated into thecamera body where they serve to restrict the movement of restrictinglevers 3 and 4 in directions A₁ and A₂, respectively, keeping hands 3aand 4a parallel to line M. Protrusions 2b and 2c of first spin lever 2engage hand portions 3a and 4a of restricting levers 3 and 4 when firstspin lever 2 is rotated in direction A₂ or A₁, respectively. Therotation of first spin lever 2, in direction A₂, rotates restrictinglever 3 so as to compress together arms 5a and 5b of spring 5 producingthe bias against the rotation. Similarly, rotation in direction A₁rotates restricting lever 4 compressing arms 5a and 5b of spring 5.Compression of spring 5 produces a force creating a bias againstrotation. Thus, first spring lever 2 is biased in the neutral positionwhere its centerline is parallel to line L where line L is orthogonal toline M which passes through the centers of stops 1c and 1b.

Operation of the switch from outside camera cover 14 is accomplishedusing operating lever 13. Rotating operating lever 13, in a direction ofarrow B₁, rotates first spin lever 2 in a direction of arrow B₂ viasecond spin lever 11. First spin lever 2 rotates brush mount board 9displacing brush 8 along substrate 7, thereby producing the electricalsignal for controlling the motor. Simultaneously, protrusion 2c moveshand portion 4a in a direction of arrow B₃ pressing tab 4b againstspring arm 5a for producing the bias against movement. The bias returnsfirst spring lever 2 to the neutral position when force is removed fromoperating lever 13.

Referring to FIG. 4, brush 8 is depicted as a multi-position switchconnecting line 7a to one of taps 7b₀ through 7b₂ that connect to aresistive divider network 7c. Voltage source 23 applies a referencepotential to resistive divider network 7c and a central processing unit20 (hereinafter CPU). Taps 7b₀ through 7b₂ supply linearly increasingvoltage potentials from resistive divider network 7c, one of which is aselected potential supplied to CPU 20 via line 7a and brush 8. CPU 20utilizes an A/D converter having voltage source 23 as a referencepotential for digital conversion of the selected potential. CPU 20controls a motor drive circuit 21, in a well known manner, based upon aconverted value of the selected potential. Motor drive circuit 21actuates a motor 22 which drives a lens focusing mechanism. A voltage ofhalf the reference potential is applied to CPU 20 when brush 8 contactscenter tap 7b₀. CPU 20 interprets this selected potential as the neutralposition and therefore maintains the focus in its existing state. CPU 20drives motor 22 rapidly in a first direction when brush 8 contacts tap7b₂ because a high potential is applied to CPU 20. Similarly, CPU 20drives motor 22 rapidly in a second direction when brush 8 contacts tap7b₁ since a low potential is selected. Taps between tap 7b₀ and taps 7b₁and 7b₂ provide selected potentials that drive motor 22 in opposingdirections at lower speeds useful when fine focusing is required.

In view of this specification, it is recognized that alternativeembodiments of the present invention may employ continuously variablepotentiometers or variable resistors to generate selected voltagepotentials for use as a motor control signals. Furthermore, it isrecognized that alternative embodiments may incorporate a non-linearrelationship between switch position and the selected potential,presenting advantages in various applications. Such alternativeembodiments are within the scope and spirit of the present invention.

Referring to FIG. 5, a schematic view of substrate 7 and brush 8 showsbrush 8 having two contacts that ride upon tap pattern 7b and line 7a.Line 7a functions as a pick-up rail. Tap pattern 7b includes taps 7b₀-7b₂ which connect to resistive divider network 7c. Movement of brush 8connects a tap to the pick-up rail pattern, thereby applying theselected potential to line 7a and CPU 20. Resistance to ground at taps7b₀ -7b₂ varies linearly with the position of brush 8 thereforeproducing a linearly increasing selected potential. Connection of brush8 to one of tap 7b₁ and tap 7b₂ provides a minimum and a maximum valueof the selected potential, respectively, initiating rapid motoroperation in one of a first and a second direction.

The operation of the switch provides a minimum and maximum selectedpotential when contacts of brush 8 are aligned on lines P₁ and P₂,respectively. First spin lever 2 is located at the neutral position whenthe contacts of brush 8 are on a line P₀, where the resistance to groundis half the maximum value and the selected potential is one half of thereference potential. The resistance to ground and the selected potentialis reduced, as brush 8 is moved in a direction towards line P₁, the lensmoves toward a first extreme focus position, for example the near focusposition. Likewise, when the resistance to ground and the selectedpotential is increased, as brush 8 is moved in a direction to line P₂,the lens moves toward a second extreme focus position, for example thefurthest or infinity focus position. Motor speed increase with theamount of displacement of brush 8 from line P₀.

The mechanism of the present invention provides a user-friendlyinterface with the camera wherein both speed and direction of focus maybe controlled by a single lever, operating lever 13. This operationproduces an ergonomically efficient means of focusing the lens providingfor ease of operation and reduced user fatigue.

Referring to FIG. 6, a characteristic of a focussing velocity v as afunction of a position of brush 8 between P₁ and P₂, as depicted in FIG.5, is shown to be linear. When brush 8 moves to positions P₁ and P₂ thelens is focused at a corresponding maximum speed, approaching the nearand infinity focus extremes respectively.

It is recognized in view of this specification that alternativeembodiments of the present invention include a brush directly contactingeither a linear or a non-linear resistive pattern, such as thoseemployed in cermet potentiometers. Furthermore, it may be realized byone skilled in the art, in light of this specification, that anelectrical signal for use in the present invention may be alternativelygenerated by means of a variable electric component wherein a resultingvaried electrical condition is sensed by a CPU. Embodiments furtherinclude the variable electric component operating in a linear slide modeor other mechanical arrangements. Additionally, while a CPU 20 is usedin the preferred embodiment, other embodiments of the present inventionmay employ alternative digital or analog control means.

Having described preferred embodiments of the invention with referenceto the accompanying drawings, it is to be understood that the inventionis not limited to those precise embodiments, and that various changesand modifications may be effected therein by one skilled in the artwithout departing from the scope or spirit of the invention as definedin the appended claims.

What is claimed is:
 1. A power focus device for a lens of a cameracomprising:a rotatable member; a voltage divider between a first andsecond reference voltage; said voltage divider having at least first,second, third, fourth, and fifth terminals; said rotatable memberincluding a switch selectively connectable to any one of said first,second, third, fourth, or fifth terminals; a central processing unit; anoutput of said switch being connectable to an input of said centralprocessing unit; a lens driver circuit; said central processing unitproducing a signal for driving said lens driving circuit; a resilientmember biasing said switch to a neutral position in contact with saidthird terminal and permitting rotation thereof from said neutralposition in a first and a second direction within a fixed angular range;said central processing unit maintaining a position of said lens whensaid switch is in said third position; said lens driving circuit drivingsaid lens in a first focussing direction at a slow and a fast speed whensaid switch moves in said first direction and contacts said second andfirst terminals, respectively; said lens driving circuit driving saidlens in a second focussing direction at a slow and a fast speed whensaid switch moves in said second direction and contacts said fourth andfifth terminals, respectively.
 2. A power focus device for a cameraaccording to claim 1, wherein:said camera includes a camera cover; saidrotatable member includes an inside member inside said camera cover; andsaid rotatable member includes a user accessible portion outside saidcamera cover effective for rotating said inside member.
 3. A power focusdevice for a camera according to claim 1 wherein said speed that saidlens driving circuit drives said lens is responsive to an angle of saidrotatable member from said neutral position.
 4. A power focus device forfocusing a lens of a camera comprising:a first switch member; a voltagedivider between a first and second reference voltage; said voltagedivider having at least first, second, third, fourth, and fifthterminals; said first switch member selectively connectable to any oneof said first, second, third, fourth, or fifth terminals; a centralprocessing unit; an output of said switch being connectable to an inputof said central processing unit; a lens driver circuit; said centralprocessing unit producing a signal applied to said lens driving circuit;a resilient member biasing said first switch member to contact saidthird terminal; said resilient member permitting movement of said firstswitch member in first and second opposed directions from said thirdterminal; said lens driving circuit inactivating said power focus devicewhen said first switch member is connected to said third terminal; saidlens driving circuit driving said lens in a first focusing direction inresponse to displacement of said first switch member from said thirdterminal in said first direction, whereby said first switch member isconnected to one of said first and said second terminal.; said lensdriving circuit driving said lens in said second focusing direction inresponse to displacement of said first switch member from said thirdterminal in said second direction, whereby said first switch member isconnected to one of said fourth and fifth terminals; said third terminalof said first switch member corresponding to an output of said voltagedivider between a minimum and maximum output of said voltage divider;and said lens driving circuit being further responsive to an amount ofmotion of said first switch member in said first and second directionsto control a speed of driving of said lens in the respective directions.5. A power focus device for focusing a lens of a camera according toclaim 4 wherein a speed of focusing varies in relation to an amount ofdisplacement of said first switch member from said third terminal.
 6. Apower focus device for focusing a lens of a camera according to claim 5wherein said speed of focusing is linearly related to said amount ofdisplacement.
 7. A power focusing device for focusing a lens of a cameraaccording to claim 4 further comprising:a lever operably linked to saidfirst switch member from a position outside said camera cover throughsaid camera cover to permit said displacement of said first switchmember; and a seal preventing fluids from entering said camera cover. 8.A power focus device for focussing a lens of a camera according to claim7 wherein:said lever includes a shaft passing through said camera cover;and said seal includes a pliable switch cover mounted on said cameracover over said lever.
 9. A power focusing device for focusing a lens ofa camera comprising:a movable switch member accessible from outside saidcamera; a voltage divider between a first and second reference voltage;said voltage divider having at least first, second, third, fourth, andfifth terminals; said movable switch member selectively connectable toany one of said first, second, third, fourth, or fifth terminals; acentral processing unit; an output of said movable switch member beingconnectable to an input of said central processing unit; a lens drivercircuit; said central processing unit producing a signal applied to saidlens driving circuit; said lens driver circuit focusing said lens infirst and second directions in response to a direction of saidbidirectional motion such that said lens driver circuit is controlled bya direction of actuation of said movable switch member; said lens drivercircuit does not focus said lens when said movable switch member isconnected to said third terminal; and said third terminal correspondingto an output of said voltage divider between a minimum and a maximumvalue of said voltage divider.
 10. A power focus device for focusing alens of a camera according to claim 9 further comprising a resilientmember biasing said movable switch member to said third terminal.
 11. Apower focusing device for focusing a lens of a camera according to claim9 wherein a speed of said focusing is responsive to an amount ofdisplacement of said movable switch member.
 12. A power focus device forfocusing a lens of a camera according to claim 11 wherein said speed offocusing is responsive to a state of said variable electrical component.